Jets fan knocks Bills fan out cold at MetLife Stadium (VIDEO)

Jets players had plenty to feel punchy about while being blown out by the Bills at MetLife Stadium Sunday. And one Jets fan in the stands took out his manly frustration on a Bills spectator with a brutal, one-punch knockout of the visitor.

TMZ posted a cell phone video of the Jets fan (in a No. 10 Chad Pennington jersey) throwing a punch in the stands in a fight with another dude in a Bills jersey. The blow appeared to knock the Bills fan unconscious. "He's still down," someone says on the video. TMZ reported the fight broke out "right after the Bills started pulling away."

Witnesses also said the fan who threw the punch exited before security came. One told the site, "The Bills fan had been shooting his mouth off before the fight and the Jets fans took exception."

It did not appear the Bills fan suffered "serious injury."

The State Police told TMZ they have "very good footage" of the entire incident from their state-of-the-art surveillance system — and warn others, "Anyone would be a fool to commit a crime inside MetLife Stadium."

J-E-T-S. Losers on the field. Losers in the stands.